Self-organizing actin patterns shape membrane architecture but not cell mechanics.

Area of Science:

• Cell Biology
• Biophysics

Background:

• Cell-free studies show actin-associated proteins organize actin filaments into dynamic patterns (vortices, asters, stars).
• Understanding actin cortex self-organization in living cells is crucial for cell mechanics and membrane dynamics.

Purpose of the Study:

• To investigate actin cortex self-organization dynamics in living HeLa cells during adhesion.
• To determine the driving forces behind actin pattern transitions and their impact on cell mechanics and membrane fluidity.

Main Methods:

• Utilized complementary microscopic techniques to observe actin cortex organization in living HeLa cells.
• Performed concomitant measurements of cell mechanics and plasma membrane fluidity.

Main Results:

• Observed a multistage process of actin pattern transitions (vortices to stars to asters) during cell adhesion.
• Identified Arp2/3 complex nucleation as the primary driver, contrasting with in vitro predictions involving myosin motors.
• Demonstrated that actin patterning alters membrane architecture independently of macroscopic cortex elasticity.

Conclusions:

• Actin cortex self-organization in living cells is a complex process driven by Arp2/3 complex nucleation.
• Cells can adjust membrane architecture via actin filament assembly without altering macroscopic mechanical properties.
• This highlights a novel mechanism for cellular adaptation and regulation.